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Accumulation of DNA damage in hematopoietic stem and progenitor cells during human aging.

Rübe CE, Fricke A, Widmann TA, Fürst T, Madry H, Pfreundschuh M, Rübe C - PLoS ONE (2011)

Bottom Line: Here we tested this hypothesis in healthy individuals of different ages by examining unrepaired DNA double-strand breaks (DSBs) in hematopoietic stem/progenitor cells matured in their physiological microenvironment.Analyzing CD34+ and CD34- stem/progenitor cells we observed an increase of endogenous γH2AX-foci levels with advancing donor age, associated with an age-related decline in telomere length.Based on these findings we conclude that age-related non-telomeric DNA damage accrual accompanies physiological stem cell aging in humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Saarland University, Homburg/Saar, Germany. claudia.ruebe@uks.eu

ABSTRACT

Background: Accumulation of DNA damage leading to adult stem cell exhaustion has been proposed to be a principal mechanism of aging. Here we tested this hypothesis in healthy individuals of different ages by examining unrepaired DNA double-strand breaks (DSBs) in hematopoietic stem/progenitor cells matured in their physiological microenvironment.

Methodology/principal findings: To asses DNA damage accumulation and repair capacities, γH2AX-foci were examined before and after exposure to ionizing irradiation. Analyzing CD34+ and CD34- stem/progenitor cells we observed an increase of endogenous γH2AX-foci levels with advancing donor age, associated with an age-related decline in telomere length. Using combined immunofluorescence and telomere-fluorescence in-situ hybridization we show that γH2AX-foci co-localize consistently with other repair factors such as pATM, MDC1 and 53BP1, but not significantly with telomeres, strongly supporting the telomere-independent origin for the majority of foci. The highest inter-individual variations for non-telomeric DNA damage were observed in middle-aged donors, whereas the individual DSB repair capacity appears to determine the extent of DNA damage accrual. However, analyzing different stem/progenitor subpopulations obtained from healthy elderly (>70 years), we observed an only modest increase in DNA damage accrual, most pronounced in the primitive CD34+CD38(-)-enriched subfraction, but sustained DNA repair efficiencies, suggesting that healthy lifestyle may slow down the natural aging process.

Conclusions/significance: Based on these findings we conclude that age-related non-telomeric DNA damage accrual accompanies physiological stem cell aging in humans. Moreover, aging may alter the functional capacity of human stem cells to repair DSBs, thereby deteriorating an important genome protection mechanism leading to exceeding DNA damage accumulation. However, the great inter-individual variations in middle-aged individuals suggest that additional cell-intrinsic mechanisms and/or extrinsic factors contribute to the age-associated DNA damage accumulation.

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Accumulation of DSBs and declining DSB repair capacities with advancing age.The number of pre-existing γH2AX-foci (upper panels), and radiation-induced γH2AX-foci at 8 hours (middle panel) and 24 hours (lower panels) after irradiation with 2 Gy was plotted against donor age, depicted separately for CD34+ and CD34− cells. Linear regression analyses were performed (solid lines) and Spearman's rank correlation coefficients (rs) were calculated. For three different arbitrary groups (age: 0/<50/>50 years) mean γH2AX-foci levels are displayed in bar graphs. Error bars represent the SE within the specific group. *Statistically significant difference to the next younger age group (p<0.05).
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pone-0017487-g002: Accumulation of DSBs and declining DSB repair capacities with advancing age.The number of pre-existing γH2AX-foci (upper panels), and radiation-induced γH2AX-foci at 8 hours (middle panel) and 24 hours (lower panels) after irradiation with 2 Gy was plotted against donor age, depicted separately for CD34+ and CD34− cells. Linear regression analyses were performed (solid lines) and Spearman's rank correlation coefficients (rs) were calculated. For three different arbitrary groups (age: 0/<50/>50 years) mean γH2AX-foci levels are displayed in bar graphs. Error bars represent the SE within the specific group. *Statistically significant difference to the next younger age group (p<0.05).

Mentions: Subsequently, we analyzed the pre-existing DSBs in CD34+ and CD34− cells derived from various stem cell sources (umbilical cord blood, growth-factor mobilized peripheral blood, bone marrow), by counting γH2AX-foci per cell. In figure 2 (upper panels) the number of γH2AX-foci was plotted against the chronological donor age, depicted separately for CD34+ and CD34− cells. In CD34+ cells obtained from umbilical cord blood (age-group 0) the number of γH2AX-foci was generally fairly low with only minor variations (0.102±0.006 foci/cell). With increasing age we observed a steady rise in the number of γH2AX-foci, with significantly elevated foci levels in the age-group of <50 years (0.184±0.015 foci/cell; p<0.001) and even higher foci levels in the age-group of >50 years (0.245±0.023 foci/cell; p = 0.046). Similar to their stem/progenitor counterpart, the more differentiated CD34− cells obtained from cord blood revealed only low γH2AX-foci levels with only minor variations (0.074±0.006 foci/cell). Moreover, γH2AX-foci analysis of CD34− cells revealed a similar increase of unrepaired DSBs with increasing donor age, with significantly elevated foci levels in the <50 (0.145±0.018 foci/cell; p≤0.001) and >50 age-groups (0.247±0.036 foci/cell; p = 0.004). These findings suggest that unrepaired DSBs accumulate continuously in hematopoietic stem/progenitor cells (CD34+) and their more differentiated progeny (CD34−) during physiological aging.


Accumulation of DNA damage in hematopoietic stem and progenitor cells during human aging.

Rübe CE, Fricke A, Widmann TA, Fürst T, Madry H, Pfreundschuh M, Rübe C - PLoS ONE (2011)

Accumulation of DSBs and declining DSB repair capacities with advancing age.The number of pre-existing γH2AX-foci (upper panels), and radiation-induced γH2AX-foci at 8 hours (middle panel) and 24 hours (lower panels) after irradiation with 2 Gy was plotted against donor age, depicted separately for CD34+ and CD34− cells. Linear regression analyses were performed (solid lines) and Spearman's rank correlation coefficients (rs) were calculated. For three different arbitrary groups (age: 0/<50/>50 years) mean γH2AX-foci levels are displayed in bar graphs. Error bars represent the SE within the specific group. *Statistically significant difference to the next younger age group (p<0.05).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3049780&req=5

pone-0017487-g002: Accumulation of DSBs and declining DSB repair capacities with advancing age.The number of pre-existing γH2AX-foci (upper panels), and radiation-induced γH2AX-foci at 8 hours (middle panel) and 24 hours (lower panels) after irradiation with 2 Gy was plotted against donor age, depicted separately for CD34+ and CD34− cells. Linear regression analyses were performed (solid lines) and Spearman's rank correlation coefficients (rs) were calculated. For three different arbitrary groups (age: 0/<50/>50 years) mean γH2AX-foci levels are displayed in bar graphs. Error bars represent the SE within the specific group. *Statistically significant difference to the next younger age group (p<0.05).
Mentions: Subsequently, we analyzed the pre-existing DSBs in CD34+ and CD34− cells derived from various stem cell sources (umbilical cord blood, growth-factor mobilized peripheral blood, bone marrow), by counting γH2AX-foci per cell. In figure 2 (upper panels) the number of γH2AX-foci was plotted against the chronological donor age, depicted separately for CD34+ and CD34− cells. In CD34+ cells obtained from umbilical cord blood (age-group 0) the number of γH2AX-foci was generally fairly low with only minor variations (0.102±0.006 foci/cell). With increasing age we observed a steady rise in the number of γH2AX-foci, with significantly elevated foci levels in the age-group of <50 years (0.184±0.015 foci/cell; p<0.001) and even higher foci levels in the age-group of >50 years (0.245±0.023 foci/cell; p = 0.046). Similar to their stem/progenitor counterpart, the more differentiated CD34− cells obtained from cord blood revealed only low γH2AX-foci levels with only minor variations (0.074±0.006 foci/cell). Moreover, γH2AX-foci analysis of CD34− cells revealed a similar increase of unrepaired DSBs with increasing donor age, with significantly elevated foci levels in the <50 (0.145±0.018 foci/cell; p≤0.001) and >50 age-groups (0.247±0.036 foci/cell; p = 0.004). These findings suggest that unrepaired DSBs accumulate continuously in hematopoietic stem/progenitor cells (CD34+) and their more differentiated progeny (CD34−) during physiological aging.

Bottom Line: Here we tested this hypothesis in healthy individuals of different ages by examining unrepaired DNA double-strand breaks (DSBs) in hematopoietic stem/progenitor cells matured in their physiological microenvironment.Analyzing CD34+ and CD34- stem/progenitor cells we observed an increase of endogenous γH2AX-foci levels with advancing donor age, associated with an age-related decline in telomere length.Based on these findings we conclude that age-related non-telomeric DNA damage accrual accompanies physiological stem cell aging in humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Saarland University, Homburg/Saar, Germany. claudia.ruebe@uks.eu

ABSTRACT

Background: Accumulation of DNA damage leading to adult stem cell exhaustion has been proposed to be a principal mechanism of aging. Here we tested this hypothesis in healthy individuals of different ages by examining unrepaired DNA double-strand breaks (DSBs) in hematopoietic stem/progenitor cells matured in their physiological microenvironment.

Methodology/principal findings: To asses DNA damage accumulation and repair capacities, γH2AX-foci were examined before and after exposure to ionizing irradiation. Analyzing CD34+ and CD34- stem/progenitor cells we observed an increase of endogenous γH2AX-foci levels with advancing donor age, associated with an age-related decline in telomere length. Using combined immunofluorescence and telomere-fluorescence in-situ hybridization we show that γH2AX-foci co-localize consistently with other repair factors such as pATM, MDC1 and 53BP1, but not significantly with telomeres, strongly supporting the telomere-independent origin for the majority of foci. The highest inter-individual variations for non-telomeric DNA damage were observed in middle-aged donors, whereas the individual DSB repair capacity appears to determine the extent of DNA damage accrual. However, analyzing different stem/progenitor subpopulations obtained from healthy elderly (>70 years), we observed an only modest increase in DNA damage accrual, most pronounced in the primitive CD34+CD38(-)-enriched subfraction, but sustained DNA repair efficiencies, suggesting that healthy lifestyle may slow down the natural aging process.

Conclusions/significance: Based on these findings we conclude that age-related non-telomeric DNA damage accrual accompanies physiological stem cell aging in humans. Moreover, aging may alter the functional capacity of human stem cells to repair DSBs, thereby deteriorating an important genome protection mechanism leading to exceeding DNA damage accumulation. However, the great inter-individual variations in middle-aged individuals suggest that additional cell-intrinsic mechanisms and/or extrinsic factors contribute to the age-associated DNA damage accumulation.

Show MeSH
Related in: MedlinePlus